Method and apparatus for growing single crystals of quartz



April 13, .1954 A. R. SOBEK ETAL 2,675,303

METHOD AND APPARATUS FOR GROWING SINGLE CRYSTALS OF QUARTZ Filed April11, 1950 3 Sheets-Sheet l 5. INVENTOR.

ANDREW R. SOBEK BY DANFORTH R. HALE Hmzw KL- hum K ATTOR N EY April 13,1954 A. R. soalzK ETAL' METHOD AND APPARATUS FOR GROWING SINGLE CRYSTALSOF QUARTZ Filed April 11, 1950 3 Sheets-Sheet 2 FIG. 2

IN VEN TOR. ANDREW R. SOBEK By DANF'ORTH R. HALE FIG. 3

ATTORNEY April 1954 A. R. SOBEK ET AL METHOD AND APPARATUS FOR GROWINGSINGLE CRYSTALS OF QUARTZ 3 Sheets-Sheet 3 Filed April 11, 1950 FIG. 6

IN V EN TOR. ANDREW R. SOBEK DANFORTH R.HALE

FIG. 7

ATTORNEY Patented Apr. 13, 1954 UNITED STATES PATENT OFFICE METHOD ANDAPPARATUS FOR GROWING SINGLE CRYSTALS OF QUARTZ Application April 11,1950; Serial No. 155,221

19 Claims. (01. 2 3-301) This invention relates to improvedapparatus forgrowing single crystals of quartz.

Ehe synthesis of single crystals of quartz has been the subject oflaboratory investigation for about 50 years. During the past 15 yearsthere has been an enormous. increase in demand for quartz crystalshaving substantial volumes of the flawless crystalline substance forelectrical uses, for example, in the frequency-determining circuits ofradio frequency oscillators and in filter circuits. This great demand,coupled: with the remoteness and unreliability of the sources of naturalquartz and the poor average quality of the natural inineral hasincreased the import tance of finding a commercially practical method ofsynthesis.

Nevertheless, it was only recently that proc-i esses for growing sing1ecrystals of quartz in commercially significant quantities have beendevised. Such a process for growing a single crystal of quartz isdescribed and claimed in application Ser. No. 94,682 for Letters Patentof the United States, filed May 21-, 1949:, in the names of Danfcrth R.Hale and Andrew R. Sobek and assigned to the same assignee as thepresent invention.

grown by exposing a quartz crystal seed under elevated temperature andpressure conditions to an aqueous medium including substantialquantitiesof an alkali metal carbonate material suchas sodium carbonate or sodiumbicarbonate. This material may be sodium carbonate having an initialmolar concentration at room temperature of approximately one to two.This aqueous medium is maintained in contact with a supply material ofcrystalline quartz under still higher temperature conditionsforeffecting transfer of silica from the supply material to the quartzseed.

In another application, Ser. No. 94,683. for Letters Patent of theUnited States, filed in the names of Danforth R.l-Ia1e and Andrew Sobekon 21, 1949, and assigned tothesame as-' signs-e as th presentinvention,there disclosed and claimed the process for growing asi-ngle crystal ofquartz which comprises placing within a pressure vessel a quartz seedand a supply materiai of crystalline quartz, filling with an a1ka.-.line aqueous medium at least one third andaprefer, ably at least aboutone half of the remaining free volume in the vessel as measured at. roomtomperature, and sealing the vessel and. heating the contents thereof toa minimum temperature b.e-. tween 375 to 575 C. The application of heatis cstinued protract d pe iod-i ti e cas In accordance with this processquartz to maintain the contents of the vessel near the supply materialappreciably hotter than the contents near the seed, the vessel and: itscontents being arranged to efiect circulation of the aqueous, medium byconvection, whereby the supply material is dissolved in the medium withgrowth of the quartz seed.

Apparatus for use. in attempting a synthesis of quartz usually has takenthe form of a bomb or autoclave. As illustrated. in the drawings of theaforementioned copending; applications, Ser. Nos. 94,682 and 94 6 83. ofwhich the present application is a continuation-impart, the autoclave isa thick-walled metal cylinder capable of withstanding elevatedtemperatures and internal pressures, and disposed with its axisvertical.

Giorgio Spezia, working in Italy some 40 years ago, used a bomb of thesame general type with the supply material disposed in a basket near thetop of the internal chamber and with a quartz seed affixed in the.chamber beneath the supply material. The upper portion of the bomb wasarranged to be heated. A warm silicate solution surrounding the supplymaterial dissolved silica,

which apparently diiiused slowly downward until itreached the seed. Thelower temperature in the neighborhood of the. seed caused the aqueousmedium to become supersaturated with respect to. silica, which thendeposited in an orderly manner on the quartz. seed. This arrangementresulted in a slow increase in weight oi the crystal. The seed crystalhad to be placed in a region where the temperature of the solution wasjust enough. lower than the temperature in the upper portion of thechamber to provide the desired growing conditions.

In the apparatus illustrated in the aforementioned copendingapplications, the silica supply material is placed near the bottom ofthe cylindrical chamber; while the seed is suspended near the top of thechamber. when the lower portion of the autoclave is heated, convectioncurrents are establishedtencling to transport silica. dissolved from thesupply material upward to the neighborhood of the. seed for depositionthereon and tending to return the cooler solution to the lower part ofthe chamber for dissolving additional silica. While apparatus of thistype has been used to grow quartz in commercially significantquantities. within. reasonable periods of time, considerable care mustbe exercised to adjust the temperatureconditions within the autoclave,nctonly for the purpose of obtaining a desirable amount ofsupersaturation with respect to silica of the aqueous medium in theneighbor-hood of 1.18

quartz seed, but also to achieve a substantial thermal circulation ofthe fluid in the autoclave without causing excessive turbulence ordestroying the temperature differential between the upper and lowerportions of the chamber. It also will appear that the distribution ofconvection currents within the vertical chamber, when maintained hotternear the bottom, will be somewhat fortuitous and may depend largely onthe precise location of the solid objects in the chamber and on rathersmall differences of temperature in the walls of the chamber. As aconsequence the tendency for a quartz seed to grow may depend to anappreciable extent upon its exact position and orientation Within thechamber, and only a rather small portion of the entire chamber mayprovide suitable. locations for the quartz seed or seeds. 7

Accordingly it is an object of the present invention to provide new andimproved apparatus for growing single crystals of quartz whichsubstantially avoids: one or more of the limitations and disadvantagesof prior apparatus of the type described."

It is another object of the invention to provide new and improvedapparatus for growing single crystals of quartz which permits easyadjustment of' the conditions suitable for the synthesis of V quartz.

It is a further object of the invention to provide new and improvedapparatus for growing quartz crystals which provides extensive regionsfor receiving siliceous supply material and in which quartz seeds may bedisposed.

It is also an object of the invention to provide new and improvedapparatus for growing single crystals of quartzin large quantities andwith commercially attractive control techniques.

' In accordance with one feature of the invention, apparatus for growingsingle crystals of quartz comprises a pressure vessel including asilica-dissolving region for receiving a supply material of crystallinequartz and including a quartz-growing region arranged to hold at leastone 'quartzcrystal seed so that'there may be disposed in the vessel afluid for dissolving therein silica-from the supply material and fordepositing therefrom quartz on the seed. This apparatus also comprisesconstricted channel means in the pressure vessel communicating betweenthe silicadissolving region and the quartz-growing region. The apparatusfurther comprises means for maintaining the fluid under elevatedtemperature and pressure conditions in the quartz-growing regionand'under still higher temperature conditions in the silica-dissolvingregion and for effecting transfer of the fluid from each of theseregions to the other thereof through the channel means. r

In accordance with another feature of the invention, the above-mentionedpressure vessel includes a silica-dissolving region in the form of achamber for receiving a siliceous supply material such as theaforementioned crystalline quartz and includes a quartz-growing regionin the form of a chamber arranged to hold the seed; in this case theconstricted channel means communicating between the silica-dissolvingchamber and the quartz-growing chamber is a plurality of pipes formingpart of the pressure vessel. In accordancewith a further aspect of theinvention, the means which functions to effect transfer of the fluidfrom each of the regions or chambers to the other thereof comprises amechanical means which also functions for efiecting dispersal within 4the quartz-growing region or chamber of the fluid so transferredthereto.

For a better understanding of the present invention, together with otherand further objects thereof, reference is had to the followingdescription taken in connection with the accompanying drawings, and itsscope will be pointed out in the appended claims.

' In the drawings,

Fig. 1 is a perspective view, partially cut away in several places, ofan apparatus for growing a single crystal of quartz embodying thepresent invention, the apparatus being shown disposed in a roughlyhorizontal plane;

Fig. 2 is a central section taken horizontally through the upperright-hand portion of the apparatus as viewed in Fig. 1;

Fig. 3 is a sectional elevation taken in the direction indicated 3, 3 inFig. 2;

Fig. 4 is a simplified plan view of another apparatus for growing asingle crystal of quartz embodying the present invention, the view beingsectionalized at the left hand side along a central horizontal plane toillustrate the internal arrangement of the several chambers and crosspipes in the apparatus;

Fig. 5 is a perspective view of one end portion of an internal linerused in the apparatus shown in Fig. 1; V

Fig. 6 is an end elevation of the liner'of Fig. 5 showing an alternativearrangement of the interior of the apparatus; and

Fig. 7 is an end view, taken similarly to the View of Fig. 6, of analternative inner liner arrangement.

Referring now to Fig. 1, there is shown in perspective a completeapparatus for growing single crystals of quartz. The quartz -growingequipment is mounted on a table H which is centrally pivoted as at l2for rocking about one of the axes of the table. The pivoting arrangementis supported on stationary brackets I 3 and I4. A slow speed motor i3 isarranged to rock the table I! by means of a rocker arm I! and aneccentric arm is having an adjustable radius. With this arrangement thetable il may be rocked about a horizontal position to extreme positionssuch as 2| and 22, shown in dashed lines, which may have anangular'relationship with the horizontal position of from severaldegrees to as much as 45 or more, depending on the effective length ofthe eccentric arm l8.

The quartz-growing apparatus proper may be secured to the table ll byany suitable means such as one or more brackets 23. It comprises apressure vessel including an elongated silicadissolving chamber 24 forreceiving a siliceous supply material 26 and including an elongatedquartz-growing chamber 2? arranged to hold at least one quartz crystalseed 28 and preferably a plurality of such seeds 23, 29, 3|, etc.

Each of the chambers 24 and 27 is provided with a removable end closure.The closure for the chamber 24 includes a central plug 33 having aninternal shoulder 34 bearing against a gasket 36. The end of the chamber24 is threaded and receives an externally threaded collar 31, the

inner end of which also bears against the gasket 36. The protruding endof the plug 33 receives a washer 38, which bears against the outer endof the collar 31. The outer end of the plug 33 also is threaded toreceive a nut 39 over the Washer 38. When the nut 39 is tightened, plug33 is drawn up to compress the gasket 36, thus effecting a pressureseal. The chamber 21 similarly acrzaaoa E: ispmvided with a, plug 4|having an. internal shoulder 42, an. inner gasket 43:, a. threaded;collar M an outer washer. 4,6,. and: a. nut 11:.

A. thermocouple well 51 extends. centrally through the plug 33.- and; issealed; thereto by a nut. and gasket. arrangement. 52; shownschematicallyon. the inside end; of the plug. The thermocouple leadsextend from. the. inner end; of the well 5|. through the welltoeigternal leads 53 for connection to. a. conventional externaltemperaturesmeasuring .cirouit, not. shown. The chamber 21. similarlyis. proraided with. a. thermocouple well 56. having. an internal. seal.51 and external leads. 5.8. The; chamber. also has. apressure-sensitive. device. 59.: of. the, aneroid type with a connectingtube 6|. extending through and sealed to the plug M. and connectingwith. a pressure gauge 62 mounted, externally eithe pres: sure vessel.Additional thermocouple; wells. 6.3 and 54 extend throu h. and are.sealed to; the other nds of the chambers 24 and 21 resp ctively, therespective h rmo ouples. being locat d Within the respectiv eh mbersanbein provid d. withleads 65.. and ti respec y for e nneo ionto ex rnal tmperature. m as rin circui s... no shown- Thus t e he mo ou l ads. 53.,58 t5, and 6 mit th c n nuous measur men o t mp r tures at. each endoreach cha ber nd e gauge 62 permits the continuous measurement of theinternal pressure in theapparatus.

The two c am e s 24 and 21 are. int rco nected in a manner describedhereinbelow so as to. form sin le v ss l adap ed. o W t stand i h. prosesures. This vessel includes a, silica-dissolving region, specificallythe major interior portions, of the chamber 24-, and a quartz-growingregion, specifically the major internal portions of the chamber 2?.Channel means, also a part of the pressure vessel, communicate betweenthe silicadissolving region and the quartz-growing region. Morespecifically, the channel means may take the form of a plurality ofpipes, for example two pipes H and I2, forming part of the pressurevessel. One of these pipes 12 may be seen in greater detail in. Figs. 2and, 3 at the regi n where it joins the chamber 21. The chamber has acounterbored and tapered hole to. receive the end of the pipe. This endof the pipe 12 seats against the counterbored portion of the hole in thecham-. her, and the taper is used to obtain a welded fillet 13', makingthe junction tight at high pres sures.

The pressure vessel including the chambers 2A and 2'! thus is arrangedso that a solvent fluid may be disposed in the pressure vessel. fordissolving in that fluid. silica from the supply mate-, rial 26 and fordepositing from that fluid quartz on the seed 23v and on the other seedsas well. This silica-transporting fluid mfi ium which is placed in thevessel may or may not include under operating conditions a liquid phasewhich fills the interior spaces in the pressure vessel, and forsimplicity of illustration no attempt has been made in the drawings to.indicate the presence of the fluid.

Means are provided for maintaining the fluid under elevated temperatureand pressure conditions in the quartz-growing chamber and under stillhigher temperature conditions in the silicadissolving chamber. Forconvenience of illustration this means is not shown in the. sectionalviews of Figs. 2 and 3. This means includes resistancewire, havingterminals 14', 15 and wound around the chamber 2-4, and also includes asimilar' winding around thechamber 2]- having terminals i-G, Fl; Thesewindings, as shown, are

made up of turns which are spaced; nearer to. gether near the ends ofthe chambers to. com-t pensate for the greater rate of heat. loss onecountered there due to. heat; transfer: through the. end surfaces. Thechambers. and H are lagged with heat-insulating coverings l8; and i9:respec-.. tively, including respective end. coverings. 8i and 3-2 whichare placed over the. closures; 'lo facilitate temperature controlthermocouples 83 and 8 42 are placed in contact with the outer surfacesof the respective chambers. These thermocouples have respective loads:86 and; 81; WhlQh. pass. throu h ceramic insulatin be ds 8.8 and as asleave the regions of. the h teh mber. wal s...

The temperature of: the. flu d he Pipe 1 i and it ls mus e ma ntained hih; en h to prevent nuc ation a d q artz depos ts n. these pipes. Forthis purpose re istance w r terminals 9! is coiled around the pipe H. Ath m upl hav n eads; 92 s p a ed at he su c of this pi to a d. iadjusting the heat i g current wh h. s c used to flew as the minals e:from a source of electric, power, not shown. Similarly the, pipe '12 iswound with a coil or". resistance wire having terminals 93 and also isprovided with a thermocouple having leads 53 i. Both pipes are laggedsimilarly to. the other outer surfaces of the pressure vessel. Ifthepipes i! and '52 are long enough, adjustment of heating currentsthrough the windings 9i and 53. can be made to control the. temperatureof the pipe walls in spite of conduction of heat between these walls andthe walls of the two chambers. In any case the pipes H and 12, shouldhave suiiiciently great lengths and sumciently small wall thick! nessesto permit substantial temperature differences between the walls of thetwo chambers without rapid conduction. of heat therebetween through thewalls of the connecting pipes.

The supply material 26 placed in the chamber 2:; preferably is ofcrystalline quartz. A microcrystalline form of quartz may be used, butfairly large lumps of scrap quartz are preferred. With such lumps arather coarse screen near the entrance to pipe H and a similar screen,not shown, across the entrance to pipe 12 serve to prevent the supplymaterial. from leaving the silica-dissolving region.

The seeds are held in the chamber 21 by an upper seed holder 95 and alower seed holder 95. As seen in Fig. 3, showing the rearmost seeds, theholder S5 carries a seed 9'! and the holder 96 carries a seed 9%. Theseeds in the holder .95 and portions of this holder are shown forclarity by dotted lines in Fig. 1, although they would not be visible inthis view because they occupy portions of the chamber 2? which have beencut away to show the internal arrangement.

Quartz seed arrangements, including seed holders similar to the holders$35" and t5 andincluding the crystal seeds, themselves, are describedand claimed in an application Ser. No. 155,222 for Letters Patent ofthe. United states, filed concurrently herewith in the name of Andrew R.Sobek and assigned to. thesame assignee as the present invention,

At the close of a quartz-growing operation a large fraction of the spacein the seed holders 95 and 96 is occupied by the quartz. crystals: intowhich the quartz seeds grow. However, it is difficult, to arrange theseed holders and seeds to utilize the peripheral spaces between. theseed holders and the inner wall of the chamber 21. If these spaces areleft open they will be by large quantities-oi fluid, which then cannotand 72, with the one region or chamber 21.

aid materially in the quartz-growing process.

Accordingly these spaces preferably are filled with a material of highheat conductivity which may be formed easily into the desired shape.Suitable liners for this purpose may be made of graphite. Such a liner99is illustrated in Figs. 13 and, as shown, has a hole to connect theinterior of the pipe 72 with the interior of the chamber 27. Liners ofthis and related types will be described in greater detail hereinbelow.

Apparatus of the type described in connection with Figs. 1-3advantageously may be used, in accordance with one .feature of theinvention, in carrying out the process for growing single crystals ofquartz which comprises disposing at least one quartz crystal seed in oneregion of a pressure vessel, such as the chamber 27 in the vessel shownin Fig. 1, and disposing a siliceous supply material in another regionof the vessel, such as the chamber 24, communicating through constrictedchannels, as'provided by the pipes TI The process further comprisesplacing an alkaline aqueous solvent fluid in the vessel, applying heatto maintain the fluid under elevated temperature and pressure conditionsin the one region or chamber 21 and under still higher temperatureconditions in the other region or chamber is and at pressures above thecritical pressure of water, and moving the pressure vessel to effecttransfer of the fluid from each of the regions to the other thereofthrough the constricted channels, whereby silica is dissolved from thesupply material by the fluid and quartz is deposited therefrom on theseed.

In accordance with another aspect of this process of the invention, asolvent fluid, such as the above-mentioned alkaline aqueous fluid, isplaced in the vessel and heat is applied to maintain the fluid underelevated temperature conditions in the one region of the vessel holdingthe seed and under still higher temperature conditions in the otherregion in which the siliceous supply material is disposed. The vesselthen is moved not only to eflect transfer of the fluid between the tworegions but also to effect dispersal within the first-mentioned oneregion of the fluid so transferred thereto.

In utilizing the apparatus of Figs. 1-3 in accordance with theseprocedures of the present invention, the supply material 25 is placed inthe chamber 24 and the screen 90 slid into place, the liner 99 is slidinto the chamber 27, and the holders 95 and 80 holding the quartz seedsare slid into the liners. An alkaline liquid, for example a one to twomolar aqueous sodium carbonate solution or other solution having acomposition formulated as discussed in the aforementioned applicationSerial No. 94,682, is poured into the vessel until the liquid occupiessome 60% to 70% of the free space available in the vessel at roomtemperature. Then the plug, gasket, and collar assemblies 33, 30, 31 andil, it, 44 are slid and turned into their respective chambers 24 and 27.The washers 38 and 46 are slipped over the exposed ends of the collarsand the nuts 3t and A! tightened until the closures are well sealed. Theheat-insulating caps Bi and 82 are put in place, and the motor I6 isstarted so as to provide, for example, a total angular excursion betweenthe extreme positions 2| and 22 of the table 11 of 20 to 40 with arocking period about minute. In order to apply heat to the solvent fluidin the vessel and maintain the desired elevated tem-" peratures of thefluid with the resulting elevated pressures, electric power is suppliedfrom sources.

notjshown to the four resistance windings. The current to the terminals'74, 15 is adjus'tedto be larger than the current to the terminals 16,.11 to provide higher temperature conditions in the silica-dissolvingchamber 2-1 than in the chamber 2?. Suitable degrees of filling of theliquid solvent medium, suitable compositions of the liquid, and suitabletemperature and pressure conditions are discussed in the aforementionedcopending applications Ser. Nos. 94,682 and 94,683.

As further examples, the liquid may fill of the free space in the vesselat room temperature and the heating windingsmay bev adjusted to providereadings of 387 C. from the thermocouple leads 53 and 66 in thesilica-dissolving chamber and readings of .378" C. from the thermocoupleleads 58 and 61 in the quartzgrowing chamber. The pressure in the vesselthen will be about 4900 p. s. i. A good yield of large, clear quartzcrystals has been obtained under these conditions over a period ofseveral weeks. Excellent results also may be obtained with a charge atroom temperature, for example, if the chamber 27 is maintained at atemperature within the range of about 350 to 370 C. while thetemperature in the chamber 2 is maintained 6 or 8 degrees higher, givinga gauge pressure of about 6000 p. s. i.

The effect of the rocking depends to some extent on the physicalcondition of the fluid in the chamber under the growing conditions.Assuming the fluid to have the properties of pure water, only a singlephase can be present in the vessel when the temperature is everywherehigher than the critical temperature of 374 C. Satisfactory operationoften can be obtained, however, under lower temperature conditions,although the higher temperatures frequently are preferable. Moreover, ifthe pressure is maintained above the critical pressure by filling theVessel with enough liquid and then heating to a sufficiently hightemperature, only one phase can be present in the vessel. The criticalpressure of pure water is 3206 p. s. i. absolute, or 3191 p. s. i.gauge. These pressure or temperature conditions, or both, easily may beexceeded as the vessel is heated, the liquid placed in the vessel insufficient quantity at room temperature having then expanded to fill theentire vessel with a fluid having no phase boundaries or liquid-vaporinterfaces. It is noted that the critical temperature and the criticalpressure may be somewhat different, and probably several percent or evenmore higher, for the system actually present in the pressure vessel,which has physical properties differing somewhat from those of purewater. However, if the fluid in the vessel is maintained at pressuresabove the critical pressure of pure water and under elevated temperatureconditicns, it is very unlikely that a vapor bubble of appreciable sizewill be present in the vessel in equilibrium with liquid solvent medium.In any event, it has been established that pressures above the criticalpressure of water are conducive to rapid growth of quartz of highquality.

If one of the cross pipes H or 12 is maintained elevated always higherthan the other cross pipe, and higher temperature conditions aremaintained in the chamber 24 than in the chamber 21 a convection flow ofthe fluid in the vessel is established with warmer fluid moving fromchamber 24 to chamber 21 through the higher cross pipe and with coolerfluid moving from chamber 21 to chamber 24 through the lower cross pipe.In such a case the provisions for heating the two chambers constitutemeans not only for maintaining the fluid under the specified elevatedtemperature and pressure conditions but also for effecting transfer ofthe fluid from each of the chambers to the other thereof through theinterconnecting channels or pipes. Operation of the apparatus in thismanner, however, has the disadvantage that substantial temperaturegradients tend to appear lengthwise of the two chambers, and thecontinuous flow of the fluid in one direction carries so much heat thatit becomes diflicult to maintain a predetermined temperature differencebetween the two chambers.

The rocking motion of the table II, described hereinabove, about an axisparallel to the cross pipes GI and 62, so that one of the cross pipes isalternately higher and lower than the other, causes convection currentsfirst in one direction and then in the other direction through each ofthe cross pipes. When the cross pipe H is higher during the rockingcycle, a small amount of the warmer, saturated fluid from thesilicadissolving chamber passes through this pipe into the chamber 2'!and distributes itself around a rather limited region near the left endof the chamber 27, as seen in Fig. 1. Later in the rocking cycle, whenthe pipe II is lower than the pipe 12, the direction of flow tends toreverse. However, at the same time the warmer fluid which has justentered the chamber "21 tends to rise in this chamber toward the otherend, which is now the higher end. Thus the second half of the rockingcycle tends to move the warmer fluid, which entered the chamber 21during the first half of the cycle, awayfrom the pipe "H, causingdispersal of the warmer fluid throughout the chamber 21 and mixing ofthe contents of the chamber. Likewise, cooler fluid from the cham berill, which enters the chamber 24 through pipe "H when the pipe H islower, tends to flow along the chamber 24 and to be mixed with thewarmer fluid in that chamber later in the rocking cycle when the pipe 7!is higher. If the rocking of the table ii is limited to reasonableangular excursions, the dispersal or mixing action just described issufficient to maintain substantially uniform temperatures throughout thelengthsof the individual chambers 24 and 2'1 without causing more fluidto pass through the pipes i! and 12 than can be assimilated by theconvection mixing within each chamber. Nevertheless, the extent of therocking should be suificient to cause an appreciable transfer of fluidby convection currents between the two chambers in spite of theobstructing action of the solid contents of the two chambers and of theconstricted openings in the connecting pipes. At the least, the

temperature differences encountered at various points along either oneof the chambers should be kept substantially smaller than the differencebetween the mean temperatures of the two chambers. Accordingly therocking arrangement constitutes mechanical means, operating by movingand more specially by rocking thepressure vessels. for effectingtransfer of the fluid from each of the chambers to the other thereofalternately in opopsite directions through the interconnecting channelsor pipes and also for eiiecting dispersal within the quartz-growinregion or chamber of the fluid so transferred thereto.

In accordance with another feature of the invention the composition andquantity of the fluid the vessel are such as to provide, under theelevated temperature and pressure conditions used, a vapor-liquid phaseboundary in the vessel with a substantial volume of the vapor phase.When this is the case the rocking causes not only convection movementsof the fluid but also causes vapor bubbles to move from the lower to thehigher ends of the chamber or chambers. This flowing motion of vaporbubbles may aid the flow of fluid between the silica-dissolving andquartzgrowing regions and promotes desirable mixing of the liquidpresent in each of these regions. The two-phase condition may beobtained, for example, with temperatures in the neighborhood of 300 to350 C. and an initial charge occupying some 50% of the free volume atroom temperature. A substantial volume of the vapor phase underquartz-growing conditions of only 5% to 10% of the internal volumecauses: good fluid transfer and mixing conditions in apparatus of thetype illustrated.

As was pointed out hereinabove, convection currents are set up in anyquart-growing apparatus, when some portions of the fluid medium in anupper part of the presure vessel are main tained substantially coolerthan other portions of the medium in a lower part of the vessel, whichtend to move in fixed patterns of flow. In other words, the maintenanceof these diiferences in temperature in the fluid medium causes thermalconvection flow of the medium in a generally fixed pattern at anypredetermined position of the vessel. These patterns of convection flowmay be quite unpredictable and may eliminate all but a small part of thepressure vessel as suitable regions for growing quartz or for dissolvingsilica. A means for moving the vessel to provide varying relativeelevations between the warmer and the cooler portions of the fluidmedium, such as the rocking arrangement shown in the Fig. 1 apparatus,has the effect of varying the patterns of convection flow of the mediumin the vicinity of the seed or seeds. thus increasing the size of theregions useful for growing quartz and also improving growing conditionsby causing flow over the growing surfaces. This effect may be obtainedin numerous types and arrangements of apparatus for growing quartzcrystals.

Thus it will be understood that, in accordance with another feature ofthe invention, the process forgrowing single crystals of quartz comrises supporting at least one quartz crystal seed in a pressure vessel,placing in the vessel a siliceous supply material, such as lumps ofcrystalline quartz, and a silica-transporting fluid medium, such as anaqueous sodium carbonate solution, and sealing the vessel and maintaininthe fluid medium therein under elevated tem erature and pressureconditions to permit solution of the supply material in the fluid mediumand deposition from the medium'of quartz on the seed, some portions ofthe fluid medium in the vessel being maintained substantially coolerthan other nortions thereof so that the difference in temperature causesthermal convection flow of the medium at predetermined positions of thevessel. This process additionally comprises moving the pressure vessel,for example by rocking the vessel about a roughly horizontal axis, toprovide varying relative elevations between the aforementioned severalportions of the medium therein to efiect varying patterns of theconvection flow in the vicinity of the seed.

Fig. 4 is a' simplified plan view illustrating a *modifledquartz-growing apparatus of the same general type as the Fig. 1apparatus.

It is assumed that the apparatus is in a generally hori zontal position,and the left-hand portion of Fig. a is sectionalized along a centralhorizontal plane to show the interior portions of the chambers andinterconnecting pipes. The Fig. 4 apparatus may be very similar to thatillustrated in Fig. 1. Consequently all details of the contents of thechambers, the heating and heat-insulating arrangements, the supportingand rocking mechanism, and the temperatureand pressure-measuring devicesare omitted from Fig. 4.

The Fig. 4 apparatus comprises an elongated silica-dissolving chamberIOI and a similar elongated quartz-growing chamber I02. The channelmeans communicating between these two chambers comprises at least foursubstantially laterally separated cross pipes I03, I04, I05, and i 00.The cross pipe construction may be as illustrated in Figs. 2 and 3 forthe apparatus shown in Fig. 1. As an example of practical dimensions forthe Fig. 4. apparatus, the elongated chambers may have an over-alllength as great as /2 feet with an internal; diameter of 6 inches and awall thickness-of stainless steel of about 1 /2 inches. The relativedimensions of the other parts may be estimated from Fig. 4, the crosspipes being separated laterally by some 3 feet from each other.Seedshaving major-surfaces with both width andlength dimensions morethan 2 inches may be used, although a greater number of smaller seedsmight prove preferable.

Apparatus constructed very similarly to that illustrated in Fig. 1 mayhave dimensions of the same order of magnitude; successful apparatus ofthis description has been used with the two elongated chambers about 3.feet long and about 3 inches in internal diameter. Using 19 seeds, eachabout 1 x 1 inches in width and length, more than 2 pounds of quartz ofgood quality has been grown in less than 40 days. The high quality ofthe quartz grown makes the product 10 to 20 times as valuable in termsof usuable volume of oscillator grade quartz than the average rawelectrical quartz of commerce.

The Fig. 4 apparatus is preferably rocked about an axis parallel to thecross pipes I03I06, the axis conveniently being located centrally withrespect to the four cross pipes. Accordingly, just as with the Fig. 1.apparatus, at one extreme position in the rocking cycle the pipes 03 andI04 will carry convection currents in one direction and the pipes E05and I06 will carry convection currents in the other direction. Ifdesired, the pipes I04 and I05 may have somewhat larger internaldiameters, or the pipes I03 and I06 may be somewhat restricted at theirentrances in order to equalize the convection currents through the fourpipes, since the hydraulic pressure heads due to the differences indensity between warmer and cooler fluid tend to be greater for the twoend pipes I03 and I06.

As noted .hereinabove, the temperature distribution within the elongatedchambers is determined by heatconduction through the walls of the cross.pipes, bythe rate of fluid transfer therethrough, and by the dispersaland mixing of the fluid transferredwithin the individual chamhere. It ispreferable thatthis dispersal be extensive enough so that not only doesthe temperature in an individual elongated chamber show little variationfrom one end of the chamher to the other, but also the concentration ofall the fluid within either one of the chambers is substantially thesame except in small regions adjacent to the openings of the crosspipes. It

is convenient to use an even number ofcross pipes so that a symmetricalarrangement will not involve a centrally located cross pipe, which wouldremain at a constant relative elevation during the rocking cycle andthus would tend to carry fluid in only one direction, if at all. When atleast four cross pipes are used, for example the four pipes shown inFig. i, any local temperature variations in the chambers due toconduction of heat through the walls of the cross pipes to or from thewalls of the chambers is minimized, since the pipes connect to thechambers at more closely spaced and more numerous points. Liicewise thefluid moving back and forth through the \pipes is removed from andinjected into the chambers so that the fluid so transferred more evenlydistributed along the lengths of the elongated chambers. When thechambers are of rather great length the use of at least four cross pipestherefore adds materially to ease of control 7 and uniformity ofoperation.

Apparatus for growing single crystals of quartz comprises, asillustrated and described hereinabove, a vessel adapted to withstandelevated temperatures and internal pressures and having an internalchamber with rounded wall portions, such as the chamber 21 of theapparatus of Figs. 1-3 or the chamber I02 of the Fig. 4 apparatus. Inaccordance with another feature of the present invention liner means isprovided in contact with at least some of the rounded wall portions ofthe internal chamber and having a central opening with substantiallyplane bounding surfaces and square corners to provide channels adaptedfor disposition therein of quartz seeds. The liner shown in Figs. 1-3constitutes such liner means. This apparatus further includes means inthe aforementioned channels in contact with the liner means forsupporting quartz crystal seeds in portions of the chamber not occupiedby the liner means. The supporting means just mentioned may take theform of the seed supports or holders and 90 shown in Figs. 1-3.

The liner 99 of the Fig. 1 arrangement is shown in perspective in Fig.5. It appears in the drawing to be fashioned from two hemicylindricalbars III and H2 with a large triangular notch I I3 in the section I I Iand a similar large triangular notch I I4 in the section H2. The twosections are placed together so that the two triangular notches meet inalignment and outline a square central opening inside the liner. Whenthe pressure vessel and the internal seed-holding chamber therewithinare elongated, as in the embodiments illustrated in the drawings, thisliner arrangement will be seen to provide an essentially four-sidedelongated working portion within the chamber. The liner assembly alsomay be seen in the end view of Fig. 6, showing the two sections III andH2 outlining a square central opening, Within the opening two sets ofseeds, an upper set including a seed Iit and a lower set including aseed 1, are supported by an upper support II8, a central support i is,and a lower support I20. The supports H0, H9, and I20 constitute analternativeform of the seed supports 05 and 96 shown in Figs. 1 and 3.The

supports H8, H9, and I20 are notched, as shown in Fig. 6, so that theupperedge of the upper seed H6 is held in the support II8, the loweredge of the upper seed H6 and the upper edge of the lower seed I H areheld in laterally spaced notches in the support H9, and the lower edgeof the lowerseed, I I1 is held in a notch in the lower support no. Theleft and right edges of the supports are held in contact with the lanebounding surfiaces of the central opening in the liner 99.

An alternative form of liner is shown in end view in Fig. 7. This linerhas two sections 12! and I22 with hemicylindrical surfaces, and thesections l2! and t2? fit together to form a cylindrical 1iner forsliding into the quartz-growing chamber. The interior of this compositeliner means has an opening, as seen in Fig. '7, with plane boundingsurfaces and square corners to provide channels adapted for dispositionthere- Mean's similar to the seed holders mentioned and illustratedhereinabove,

in of quartz seeds.

and of conventional mechanical construction, are provided in the channelwithin the liner means and in contact with the liner means to supportquartz seeds such as seeds l23l26 shown in Fig. 7. An additional seedI21 may be disposed in the "central part of the opening in the liner. Itwill be apparent to one skilled in the art who is familiar ite by simpleand inexpensive machining opei ations. The use of graphite has the addedadvantage that the material is frangible. Occasionally difiiculty isexperienced in removing the seed holders from the chambers, althoughordinarily the graphite liner means of the type illustrated serve veryconveniently for insertion and removal of the seed holders. Ifnecessary, however, the frangible graphite liner may be broken up andthe crystals removed from the chamber without damage to the crystals orto the pressure vessel.

While there have been described what at pie-5' ent are considered to bethe preferred embodiments of this invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention. It is aimed, therefore, inthe appended claims to cover all such changes and modifications whichfall within the true spirit and scope of the invention.

What is claimed is:

1. Apparatus for growing single crystals of quartz comprising: anelongated vessel adapted to withstand elevated temperatures and internalpressures and having an elongated internal chamber with rounded wallportions, heat-conducting liner means in contact with at least some ofsaid rounded wall portions and having a central opening providing anessentially four-sided elongated working portion within said chamber,and means in contact with said heat-conducting liner *means forsupporting quartz crystal seeds in portions of said chamber not occupiedby said liner means.

2. Apparatus for growing single crystals of quartz comprising: a vesseladapted to withstand elevated temperatures and internal pressures andhaving an internal chamber with roundedwall portions, a graphite lineriii-contact with "at least soinec'f said rounded wall portions andhaving Cir 14 a central opening with substantiall plane boundingsurfaces, and means in contact with said liner for supporting quartzcrystal seeds in portions of said chamber :not occupied by said liner.

3. Apparatus for growing single crystals of quartz comprising: a vesseladapted to withstand elevated temperatures and internal pressures andhaving an internal chamber with rounded wall portions, linerineans incontact with at least some of said rounded wall portion and having a central opening with plane bounding surfaces and square corners to providechannels adapted for disposition therein of quartz seeds, and means insaid channels in contact with said liner means for su porting suchquartz seeds in portions of said chamber not occupied by said linermeans.

4. Apparatus for growin single crystals of quartz comprising: a vesseladapted to withstand elevated temperatures and internal pressures andhaving an internal chamber with rounded wall portions. liner means incontact with at least some of said rounded wall portions and having asubstantially square central opening, and means in contact with saidliner means for supporting quartz crystal seeds in portions of saidchamber not occupied by said liner means.

5. The process for growing single crystals of quartz, comprising:disposing at least one quartz crystal. seed in one region of a pressurevessel and a siliceous supply material in another region of said vesselcommunicating through constricted channels with said one region andplacing a sol vent iiuid in said vessel; applying eat to maintain saidfluid under elevated temperature and pressure conditions in said oneregion and under still higher temperature conditions in said otherregion; and moving said vessel to eiiect transfer of said fluid fromeach of said regions to the other thereof through said channels and toeffect dispersal within said first-rnentioned one region of the fluid sotransferred thereto, whereby silica is dissolved from said supplymaterial by said fluid and-cfuartz is deposited therefrom on said seed.

'6. The process for growing single crystals of quartz, comprising:disposing at least one quartz crystal seed in one region of a pressurevessel and a siliceous supply material in another region of said vesselcommunicating through constricted channels with said one region andplacing a solvent fluid in said vessel; applying heat to maintain saidfluid under elevated temperature and pressure conditions in said oneregion and under still higher temperature conditions in said otherregion; and moving said vessel to eiieet transfer of said fluid fromeach of said regions to the other thereof alternatively in oppositedirections through said channels and to eiiect dispersal within saidfirst-mentioned one region of the fluid so transferred thereto, wherebysilica is dissolved from said supply material by said fluid and quartzdeposited therefrom on said seed.

7. The process for growing single crystals of quartz, comprising:disposing at least one quartz crystal seed in one region of a pressurevessel and a siliceous supply material in another region of said. vesselcommunicating through constricted channels with said one region andplacing an alkaline aqueous solvent fluid in said vessel; applying heatto maintain said fluid under elevated temperature and pressureconditions in said one reg-ion and under still higher temperatureconditions in said other region and at pressures above the criticalpressure of water; and moving said vesselto efieettransfer ofsaid fluidfrom each of i 15 said regions to the other thereof through saidchannels, whereby silica is dissolved from said supply material by saidfluid and quartz is deposited therefrom on said seed.

8. The process for growing single crystal of quartz, comprising:disposing at least one quartz crystal seed in one region of a pressurevessel and a siliceous sup-ply material in another region of said vesselcommunicating through constricted channels with said one region andplacing an aqueous solvent fluid in said vessel; applying heat tomaintain said fluid under predetermined elevated temperature andpressure conditions in said one region and under still highertemperature conditions in said other region, the composition andquantity of said aqueous fluid being such as to provide under saidtemperature and pressure conditions a vapor-liquid phase boundary insaid vessel with a substantial volume of the vapor phase; and movingsaid vessel to effect transfer of said fluid from each of said regionsto the other thereof through said channels, whereby silica is dissolvedfrom said supply material by said fluid and quartz is depositedtherefrom on said seed.

9. The process for growing single crystals of quartz, comprising:disposing at least one quartz crystal seed in one region of a pressurevessel and a siliceous supply material in another region of said vesselcommunicating through constricted channels with said one region andplacing a solvent fluid in said vessel; applying heat to maintain saidfluid under elevated temperature and pressure conditions in said oneregion and under still higher temperature conditions in said otherregion; and rocking said vessel to effect transfer of said fluid byconvection currents from each of said regions to the other thereofthrough said channels and to effect dispersal within said one region byconvection movements of the fluid so transferred thereto, whereby silicais dissolved from'said supply material by said fluid and quartz isdeposited therefrom on said seed.

' 10. The process for growing single crystals of quartz, comprising:disposing at least one quartz crystal seed in one region of a pressurevessel and a siliceous supply material in another region of said vesselcommunicating through constricted channels with said one region andplacing a solvent fluid in said vessel; applying heat to maintain saidfluid under elevated temperature and pressure conditions in said oneregion and under still higher temperature conditions in said otherregion; and rocking said vessel so that one of said channels isalternately higher and lower than another of said channels to effecttransfer of said fluid by convection currents from each of said regionsto the other thereof through said channels and to effect dispersalwithin said one region by convection movements of the fluid sotransferred thereto, whereby silica is dissolved from said supplymaterial by said fluid and quartz is deposited therefrom on said seed.

1. Apparatus for growing single crystals of quartz, comprising: apressure vessel including a silica-dissolving chamber for receiving asiliceous supply material and including a quartzgrowing chamber arrangedto hold at least one quartz crystal seed so that there may be disposedin said vessel a fluid for dissolving therein silica from said supplymaterial and for depositing therefrom quartz on said seed; a pluralityof pipes forming part of said pressure vessel and communicating betweensaid silica-dissolving chamber and said quartz-growing chamber; meansfor maintaining said fluid under elevated temperature and pressureconditions'in said 'quartzgrowing chamber and under still highertemperature conditions in said silica-dissolvingchamber; and mechanicalmeans for effecting transfer of said fluid from each of said chambers tothe other thereof through said pipes and for effecting dispersal withinsaid quartz-growing chamber of the fluid so transferred thereto.

12. Apparatus for growing single crystals of quartz, comprising: apressure vessel including a silica-dissolving chamber for receiving asiliceous supply material and including a quartz-growing chamberarranged to hold at least one quartz crystal seed so that there may bedisposed in said vessel a fluid for dissolving therein silica from saidsupply material and for depositing therefrom quartz on said seed; twopipes forming part of said pressure vessel and communicating betweensaid silica-dissolving chamber and said quartz-growing chamber; meansfor maintaining said fluid under elevated temperature and pressureconditions in said quartz-growing chamber and under still highertemperature conditions in said silica dissolving chamber; and mechanicalmeans for effecting transfer of said fluid from each of said chambers tothe other thereof through said pipes and for effecting dispersal withinsaid quartz-growing chamber of the-fluid so transferred thereto.

13. Apparatus for growing single crystals of quartz, comprising: apressure vessel including an elongated silica-dissolving chamber for receiving a siliceous supply material and including an elongatedquartz-growing chamber arranged to hold at least one quartz crystal-seedso that there may be disposed in said vessel a fluid for dissolvingtherein silica from said supply material and for depositing therefromquartz on said seed; two pipes forming part of said pressure vessel,communicating between said silica-dissolving chamber and saidquartz-growing'chamber, and joined to each one of said elongatedchambers at points spaced substantially apart therealong; means formaintaining said fluid under elevated temperature and pressureconditions in said quartz-growing chamber and under still highertemperature conditions in said silica-dissolving chamber; and mechanicalmeans for effecting transfer of said fluid from each of said chambers tothe other thereof through said pipes and for effecting dispersal withinsaid quartz-growing chamber of the fluid so transferred thereto.

14. Apparatus for growing single crystals of quartz, comprising: apressure vessel including a silica-dissolvingregion for receiving asupply material of crystalline quartz and including a quartz-growingregion arranged to hold at least one quartz crystal seed so that theremay be dis posed in said vessel a fluid for dissolving therein silicafrom said supply material and for depositing therefrom quartz on saidseed; constricted channel means in said vessel communicating betweensaid silica-dissolving region and said quartz-growing region; and meansfor maintaining said fluid under elevated temperature and pressureconditions in said quartz-growing region and under-still highertemperatureconditions in said silica-dissolving region and for effectingtransfer of said fluid from each of said regions to the other therofthrough said channel means. 7

15. Apparatus for growing single crystals of quartz, comprising: apressure vessel including a silica-dissolving chamber for receiving asupply material of crystalline quartz. andincluding a quartz-growingchamber arranged to hold at least one quartz: crystal seed so that theremay be disposed in said vessel a fluid for dissolving therein silicafrom said supply material and for depositing therefrom quartz on saidseed; a plurality of pipes forming part of pressure vessel andcommunicating between said silica-dissolving chamber and quarta-growingchamber; and means maintaining said under elevated temperature andpressure conditions in said quartz-growing chamber and under stillhigher temperature conditions in said silica-dissolving chamber and foreffecting transfer of said fluid from each of said chambers to the otherthereof through said pipes.

16. Apparatus for growing single crystals of quartz, comprising: apressure vessel including an elongated silica-dissolving chamber forreceiving a siliceous supply material and including an elongatedquartagroring chamber arranged to hold plurality of quartz crystal seedsso that there may be disposed in said vessel a fluid for dissolvingtherein silica from said supply material and for depositing therefromquartz on said seeds; two generally parallel pipes forming part of saidpressure vessel, communicating between said silica-dissolving chamberand said quartzgrowing chamber, and joined to each one of said elongatedchambers at points spaced substantially apart thereaiong, said pipeshaving sufliciently great lengths and suldciently small wall thicknessesto permit substantial temperature difierences between the Walls said twochambers Without rapid conduction of heat therebetween; means forheating said two chambers and said pipes to maintain said fluid in saidvessel under elevated temperature and pressure conditions andsubstantially Warmer in said silica-dissolving chamber than in saidquartz-growing chamber; and mechanical means for rocking said pressurevessel about an axis generally parallel to said pipes, with said twochambers and said pipes disposed in a roughly horizontal plane at themean position of said vessel, to effect transfer of said fluid from eachof said chambers to the other thereof by convection currents alternatelyin opposite directions through said pipes and to effect dispersal offiuid so transferred by convection currents in lengthwise directionswithin the respective elongated chamber to which such fluid r istransferred to keep any temperature differences in the fluid in each oneof said two elongated chambers small compared with the differencebetween the mean temperatures of the fluid in said two chambers.

17. Apparatus for growing single crystals of quartz, comprising: apressure vessel including an elongated silica-dissolving chamber forreceiving a siliceous supply material and including an elongatedquartz-growing chamber arranged to hold at least one quartz crystal seedso that there may be disposed in said vessel a fluid for dissolvingtherein silica from said supply material and for depositing therefromquartz on said seed; a plurality of pipes forming part of said pressurevessel and communicating between said silica-dissolving chamber and saidquartz-growing chamber; means for maintaining said fluid under elevatedtemperature and pressure conditions in said quartz-growing chamber andunder still higher temperature conditions in said silicadissolvingchamber; and mechanical means for rocking said vessel about an axisroughly parallel to the axes of said pipes to effect transfer of saidfluid convection currents from each of said chambers to the otherthereof through pipes and to effect dispersal within quar -growingchamber by convection movements the fluid so transferred thereto.

18. The process for growing single crystals of quartz, comprising:supporting at least one quartz crystal seed in a pressure vessel;placing a siliceous supply material and a silica-transporting fluidmedi" n in vessel; sealing said vessel and maintaining fluid mediumtherein under elev... 2d temperature and pressure conditions to permitsolution of said supply material in said fluid medium and depositionfrom said medium of uartz?- on said seed, some portions of said fluidmedium in said vessel o ing maintained substantially cooler than otherportions thereof so that the dirference in temperature causes thermalconvection flow of said medium at predetermined positions of saidvessel; and moving said vessel to provide varying relative elevationsbetween said several portions or" said medium therein to efiect varyingpatterns of said convection flow in the vicinity of said seed.

19. The process for growing single crystals of quartz, comprising:supporting at least one quartz crystal seed in a pressure vessel;placing a siliceous supply material and a silica-transporting fluidmedium in said vessel; sealing said vessel and maintaining said fluidmedium therein under elevated temperature and pressure conditions topermit solution of said supply material in said fluid medium anddeposition from said medium of quartz on said seed, some portions ofsaid fluid medium in said vessel being maintained substantially coolerthan other portions thereof so that the diilerence in temperature causesthermal convection flow of said medium at predetermined positions ofsaid vessel; and rocking said vessel about a roughly horizontal axis toprovide varying relative elevations between said several portions ofsaid medium therein to eiiect varying patterns of said convection flowin the vicinity of said seed.

Graw-Hill Book 00., N. Y 3rd Ed, 1950, page 1257, Fig. 58.

Swinnerton: Report of Investigations in the European Theater, PB Report28897, Nov. 8. 1946, page 5, Fig. 4.

5. THE PROCESS FOR GROWING SINGLE CRYSTALS OF QUARTZ, COMPRISING:DISPOSING AT LEAST ONE QUARTZ CRYSTAL SEED IN ONE REGION OF A PRESSUREVESSEL AND A SILICEOUS SUPPLY MATERIAL IN ANOTHER REGION OF SAID VESSELCOMMUNICATING THROUGH CONSTRICTED CHANNELS WITH SAID ONE REGION ANDPLACING A SOLVENT FLUID IN SAID VESSEL; APPLYING HEAT TO MAINTAIN SAIDFLUID UNDER ELEVATED TEMPERATURE AND PRESSURE CONDITIONS IN SAID ONEREGION AND UNDER STILL HIGHER TEMPERATURE CONDITIONS IN SAID OTHERREGION; AND MOVING SAID VESSEL TO EFFECT TRANSFER OF SAID FLUID FROMEACH OF SAID REGIONS TO THE OTHER THEREOF THROUGH SAID CHANNELS AND TOEFFECT DISPERSAL WITHIN SAID FIRST-MENTIONED ONE REGION OF THE FLUID SOTRANSFERRED THERETO, WHEREBY SILICA IS DISSOLVED FROM SAID SUPPLYMATERIAL BY SAID FLUID AND QUARTZ IS DEPOSITED THEREFROM ON SAID SEED.14. APPARATUS FOR GROWING SINGLE CRYSTALS OF QUARTZ, COMPRISING: APRESSURE VESSEL INCLUDING A SILICA-DISSOLVING REGION FOR RECEIVING ASUPPLY MATERIAL OF CRYSTALLINE QUARTZ AND INCLUDING A QUARTZ-GROWINGREGION ARRANGED TO HOLD AT LEAST ONE QUARTZ CRYSTAL SEED SO THAT THEREMAY BE DISPOSED IN SAID VESSEL A FLUID FOR DISSOLVING THEREIN SILICAFROM SAID SUPPLY MATERIAL AND FOR DEPOSITING THEREFROM QUARTZ ON SAIDSEED; CONSTRICTED CHANNEL MEANS IN SAID VESSEL COMMUNICATING BETWEENSAID SILICA-DISSOLVING REGION AND SAID QUARTZ-GROWING REGION; AND MEANSFOR MAINTAINING SAID FLUID UNDER ELEVATED TEMPERATURE AND PRESSURECONDITIONS IN SAID QUARTZ-GROWING REGION AND UNDER STILL HIGHERTEMPERATURE CONDITIONS IN SAID SILICA-DISSOLVING REGION AND FOREFFECTING TRANSFER OF SAID FLUID FROM EACH OF SAID REGIONS TO THE OTHERTHEREOF THROUGH SAID CHANNEL MEANS.